1. Field of the Invention:
The present invention relates to a sandwich plate composed of a pair of transparent plates such as glass, synthetic resin or the like, and a transparent interlayer of synthetic resin, said sandwich plate being rendered capable of heat reflection. The heat reflecting sandwich plate is suitable as vehicle and building window glass.
2. Description of the Prior Art:
There has been known sandwich glass made up of a pair of glass sheets (made by, for example, float process) bonded together with an interlayer of transparent synthetic resin such as polyvinyl butyral. The sandwich glass of such multilayered structure has high strength and safety owing to the interlayer's ability to prevent the glass plates from shattering in the event of breakage.
A disadvantage of the sandwich glass used as vehicle and building window glass is that it transmits a large amount of solar radiant energy into the vehicle and building, causing the room temperature to rise unnecessarily, particularly in summer.
There is disclosed in U.S. Pat. No. 4,337,990 a heat reflecting glass prepared by forming a first metal oxide layer, a noble metal layer, and a second metal oxide layer consecutively on a glass sheet. The first and second metal oxide layers have almost the same thickness so that the three layers give rise to, by their light interference, a low reflectivity for light of wavelength 550 nm(nanometer) having a high visual sensitivity and yet give rise to a high transmittance for visible light.
The heat reflecting glass disclosed in the above-mentioned U.S. Patent gives a reflective spectrum which indicates the strong reflection in the longer (red) side and shorter (blue) side of the visible region. This spectral characteristic causes the heat reflecting glass to produce a dazzling reflected ray of purplish color for the incident rays on either sides. Because of this colored reflected rays, the heat reflecting glass as vehicle and building window glass is out of harmony with the exterior of the vehicle and building.